A conventional actuator 10 for a diaphragm valve is depicted in FIG. 1. In a typical fashion, a piston 14 connected to a stem 16 moves up and down within an actuator housing 18. The stem 16 is, directly or through the use of an adaptor 19, in contact with a diaphragm 20, which closes or opens the valve 12 according to the piston position. The piston 14 is biased to a normal position by the force of a spring 22. When a pressurized fluid such as air is introduced on the side of the piston opposed to the spring 22, the piston 14 moves under the air pressure, which pulls on the diaphragm 20, either opening the valve 12 as in the case of the valve shown in FIG. 1, or closing the valve. When the air pressure is released, the spring 22 returns the piston 14 back to its normal position, which in turn pushes on the diaphragm 20 and reverses the opening, or closing, of the valve 12. The air is routed through air inlet and exhaust ports 24 that are an integral part of the actuator 10.
The diaphragm 20 of this type of valve is positioned between the valve body 26 and a bonnet 28, which is a flange used to secure the actuator 10 to the valve body 26. As shown, the bonnet 28 is an integral part of the actuator 10.
Because of the commercial importance of being able to retrofit actuators to older valves, the design of the valve flange has not evolved over the years. Consequently, mostly because of a bolt pattern of the standard valve flange, it is possible to install the actuator in only two positions, at 180 degrees from each other. In many applications, the typical housing construction, with its integral air inlet and exhaust ports, dictates the orientation of the actuator, due to the restrictions in routing the associated piping to the ports. However, since only two different orientations are possible, often neither orientation is ideal, given the space constraints in the installations. To alleviate this problem, additional piping components such as swivel connectors have been mounted to the air inlet ports. However, these take up more space than may be convenient in some installations, and they are also somewhat limited in their orientation.
Another problem with known diaphragm valve actuators is that they have to be made specifically for each type of valve, depending on the size of the flange, the bolt pattern, the length of stroke required to activate the valve, and whether the valve should be normally closed or open (or modulating). Consequently, a multitude of different models of actuators needs to be manufactured and held in inventory.
There is therefore a clear need for an improved actuator suitable to operate diaphragm valves and other valves that have a linear actuator.